Home » Our Work » Regulating Toxic Pollutants

Map of PCB discharges to San Francisco Bay

This map highlights known sources and pathways of polychlorinated biphenyls (PCBs) in the San Francisco Bay Area. The size and color of the data points relate to the magnitude of potential annual discharges relative to those from similar sources. Hover over the data points to find out the estimated amount of PCBs delivered from a given source and scroll down to learn more about this data.

* Permitted discharges do not reflect actual PCB discharges from municipal or industrial dischargers. In support of the 2008 PCB TMDL, municipal wastewater agencies were estimated to discharge 2.3 kg of PCBs per year. Yet these facilities are permitted under individual NPDES permits to discharge a total of about 10.42 kg/yr. Find out more about this estimate below.
** In total, industrial dischargers in the Bay Area are permitted to deliver approximately 0.68 kg/yr of PCBs to San Francisco Bay, pursuant to their individual NPDES permits. However, the 2008 PCB TMDL estimated these facilities discharge approximately 0.035 kg/yr.

About This Data

The data presented on this map is based on the 2008 Total Maximum Daily Load (TMDL) for Polychlorinated biphenyls (PCBs) and supporting documents.

Subsequent to approval of the PCB TMDL, in 2011 the San Francisco Regional Water Quality Control Board (Regional Board) issued Order No. R2-2011-0012. This Order amended the National Pollutant Discharge Elimination System (NPDES) permit for most wastewater discharges of mercury to San Francisco Bay and served to add or revise PCB effluent limits for these dischargers. Average monthly effluent limits and daily maximum effluent limits are contained in the document for each permitted discharger of PCBs to San Francisco Bay, which are to be used for assessment of permit compliance.

Effluent limits for PCBs are presented in the Order in units of micrograms/liter and indicate the maximum PCB concentrations that should be found in wastewater, based on periodic sampling. In addition, the design flow for these facilities was contained in the order, which approximates daily wastewater discharges from these facilities. A facility's design flow was used in conjunction with average monthly effluent limits to calculate permitted annual discharges of PCBs for each of the wastewater facilities. Coordinates of effluent discharge points of each municipal and industrial discharger were based on those from the 2006 Mercury TMDL for San Francsico Bay, yet are assumed to be valid for PCB discharges as well.

For urban stormwater, estimates of annual discharges were based on the PCB TMDL itself. Regional Board staff estimate that urban stormwater agencies now discharge approximately 20 kg of PCBs per year to San Francisco Bay - representing a large proportion of the total annual load of about 33 kg. In order to meet the goal of the TMDL to reduce total PCB loading to 10 kg/yr stormwater agencies must reduce their discharges to 10% of the current load 2028, or 2 kg/yr. Although current estimates for individual stormwater agencies were not provided, the future allocation for each county was presented in the TMDL. To estimate current loading these figures were simply scaled by a factor of 10 to provide rough estimates of current PCB loads associated with urban stormwater from each Bay Area county.

 

For questions or comments about this map please contact Ian Wren (ian@baykeeper.org)